In short, assuming that Jether's name is a pun of "Jeff's Brother", just like how Slester's name is a pun of "Slender's Sister", as well as the fact that by "Jeff" it's 100% implies Jeff the Killer, & the fact that Jeff ACTUALLY canonically has a brother, both in OG creepypasta AND in FNaTI universe(at least it was mentioned in his EXTRAS description in Oblitus Casa. The only difference is that FNaTI Jeff's bro is called Louis Hodek, instead of Luis Woods), my theory is that Jether LITERALLY IS Jeff's brother, or at least a ghost of him, who now inhabbits this Treasure Island & is technically an Abandoned Enigma equivalent of GOD/UO, being a leader & protector of those suits(not only he looks like a GOD & Slester being mixed together, but his name being a refference to Slester's name may be a refference to the fact that GOD's name was originally intended to be "Slester", until it got given to a separate character. Tho we have "Corrupted Mickey", who is ).

You may ask "but how the hell did Louis ended up on Treasure Island out of all places". Well....unfortunately, i can't give you a clear answer to this question. In fact, this actually kinda even fits to the nature of Abandoned Enigma. Like seriously, i'm pretty sure that even NLLN & his team themselves could just don't really care about that—they just were like "oh, guys, did you heard of that Jeff the Killer creepypasta? Let's make a refference to that in our game!!1 :D", & just didn't cared about properly explaining or giving any context to that. They just added a tasteless refference.....just cuz they can! Cuz they are dumb teenagers, just like ME!😅

(But anyways, im pretty sure that this theory is 100% wrong & i'm just tries to overcomplicate a simple small refference that probably means nothing to the lore. Just like AE itself was probably just a simple anniversary project with nothing important being added to the story. Anyway, dear Radiance Team, with all my respect to you & my hype for 6.5, plz, DONT TAKE THESE SPECULATIONS TOO SERIOUSLY, I'm just making such theories for fun)

+I needed this post as an excuse for downloading these 2 fanarts of Jeff & Luis being together :3